No abstract

Sustainable polymers are important alternatives to plastics and elastomers derived from petroleum resources. Poly­(lactide) (PLA), a commercially available sustainable plastic, is a well-known success story. However, PLA lacks ductility and toughness, limiting the number of potential uses. In this study, small amounts of a liquid poly­(ethylene oxide)-block-poly­(butylene oxide) (PEO-PBO) diblock copolymer additive were blended with PLA to enhance its toughness and ductility. The incorporated PEO-PBO diblock copolymers generated a macrophase-separated morphology with particle diameters of 0.2–0.9 μm, and nearly matched refractive indices of PLA and PEO-PBO led to retention of optical transparency. Addition of just 1.8 wt % PEO-PBO into PLA led to a 20-fold increase in toughness, measured as the area under the stress–strain data in tension without affecting the bulk elastic modulus of the plastic. The micromechanical deformation process of the PEO-PBO/PLA blend was investigated via in situ small angle X-ray scattering during tensile testing. The total volume of the crazed material was proportional to the total surface area of the dispersed PEO-PBO particles, and both quantities increased with increasing PEO-PBO loading. Increasing the PEO-PBO loading also resulted in (A) an increase in particle size, causing a decrease in the craze initiation stress, and (B) an increase in fibril spacing, indicating a lower craze propagation stress. Furthermore, craze development was found to be independent of aging time. As a result, the PEO-PBO/PLA blend was able to remain ductile and tough for up to 114 days, exhibiting a 10-fold increase in elongation at break and toughness compared to neat PLA, which becomes brittle in less than 2 days. These results demonstrate that designing additives that promote deformation by crazing is an effective way to overcome the aging-induced embrittlement of glassy polymers.

Bi-self-doped BiVO (Bi-BVO) nanotubes with p-n homojunctions are fabricated via an oxygen-induced strategy. Calcinating the as-spun fibers with abundant oxygen plays a pivotal role in achieving Bi self-doping. Density functional theory calculations and experimental results indicate that Bi self-doping can narrow the band gap of BiVO, which contributes to enhancing light harvesting. Moreover, Bi self-doping endows BiVO with n- and p-type semiconductor characteristics simultaneously, resulting in the construction of p-n homojunctions for retarding rapid electron-hole recombination. Benefiting from these favorable properties, Bi-BVO exhibits a superior photocatalytic performance in contrast to that of pristine BiVO. Furthermore, this is the first report describing the achievement of p-n homojunctions through self-doping, which gives full play to the advantages of self-doping.

Well-dispersed polyaniline–poly(vinylpyrrolidone) (PANI–PVP) nanocomposite was synthesized through dispersion polymerization and then used as a novel additive to prepare a polysulfone (PSf)/PANI–PVP nanocomposite membrane via immersion precipitation process. During membrane formation, a portion of PVP acted as a pore-forming agent while another PANI–PVP nanocomposite, combined by hydrogen bonds between carbonyl groups of PVP and N-hydrogen groups of PANI, acted as a hydrophilic modification agent. The addition of PANI–PVP nanocomposite increased membrane surface pore size, porosity, and hydrophilicity. Pure water fluxes of PSf/PANI–PVP nanocomposite membranes were 1.8–3.5 times that of PSf membrane with a slight change of bovine serum albumin (BSA) rejection. The membrane antifouling property was examined by the cross-flow ultafiltration using BSA solution as the model system. The results of flux decline behavior and flux recovery ratio showed that PSf/PANI–PVP nanocomposite membranes had an excellent antifouling property. Compared with PSf/PVP membranes prepared using PVP as the additive, PSf/PANI–PVP nanocomposite membranes processed higher pure water flux and better hydrophilicity, antifouling property, and stability.